This invention relates to a novel organoboron complex initiator system and an acrylic adhesive composition containing this initiator. More particularly this invention involves a two-part initiator system comprising in one-part a stable organoboron amine complex and in the second part an organic acid destabilizer or activator. This initiator system is especially useful in elastomeric acrylic adhesive compositions.
Adhesive compositions including acrylic adhesives such as solutions of elastomeric polymers in soluble polymerizable acrylic or methacrylic monomers are well known in the art. These compositions which are especially known for their toughening properties generally include a redox system which comprises a catalyst or initiator, an accelerator and an activator to initiate cure, as well as other additives such as adhesion promoters, chelators, cross-linking agents, thickeners and plasticizers. Two-part acrylic adhesives where an activator is added as a separate second component are widely used and are known for curing speed as well as toughness. The catalyst or initiator typically used in these adhesives are free-radical initiators of the organic peroxy or hydroperoxy type, perester or peracid type.
Many known adhesive systems, such as the epoxies, require a thermal cure to obtain desirable properties, while others that do not, usually require prolonged cure times. In comparison, the adhesive composition with organoboron amine complex initiator of this invention cures at room temperature and reaches high tensile strength in a short period of time. Additionally, the adhesive composition of this invention has shown exceptional stability on ageing while exhibiting both high tensile strength and high peel strength.